A flight control actuator is used on an aircraft to modify one or more flight parameters by driving a flight control surface.
Traditionally, the flight control system sends a command to an electric motor drive which, in turn, powers an electric motor which provides a rotational output that is used to operate the actuator. The part of this system that is most prone to failure is the electronics that powers the motor, due to the high temperatures cycling experienced. As such, it is known to use two separate motors and motor drives to power the actuator to provide redundancy in case one motor drive fails or one motor jams.
A speed summing device can be used to combine the rotations of the two motors to give an output for operating the actuators. However, if one of the motor drives fails, this can cause the whole device to become non-operational as the rotational input of the operational motor can cause the failed motor to be driven backwards, instead of this rotation being transmitted to the output shaft of the speed summing device.
Various electromechanic braking arrangements have been proposed to prevent the failed motor being back-driven but these brakes can add excess weight and complexity to the system.
The present disclosure seeks to address at least some of these issues.